Between stress and depression your body is probably asking "what in heck is going on here!?!" Diet and lifestyle changes may not be enough to get you over the hump. Not sure if anyone has asked, so what are you doing for yourself? It's easy when you're a caregiver to focus entirely on the patient. But you have needs too. If you apply yourself entirely to the needs of your sick loved one, eventually you'll burn out and be no good to anyone. Learning to take care of yourself while taking care of your patient and the rest of your family is one of the biggest challenges to caregiving.
Sleeping may be your bodies way of saying "I need you to take care of me." The interesting thing is that sleep itself may not be the best/only solution. What your body may need is "me" time. Do you like to take walks? Watch soaps? Read books? Chat with friends? Play bridge? Etc? Make sure you alot time for this sort of thing, whatever activities you like to do, keep doing them. It will help you stay healthy and strong. Vitamins can really only do so much. Your body has limits that won't necessarily respond to a quick fix, at least not in the long term. Taking time for yourself, difficult as it may be, is your best friend. Personally, I find that I have to schedule myself, put things on my calendar that are specifically devoted to getting away from caregiving. Doesn't have to be anything major, or time consuming. Sometimes I swim for an hour. Or get coffee with a friend. Or do a crossword puzzle. Letting your brain come out of the all consuming stress state that can be caregiving is valuable.
Physiologically, one of the things that can happen to a caregiver over time is related to the endocrine system. When your body is stressed, your immune system tends to be compromised. If your body is stressed for a short period of time, it's ok because adreneline gets you through. But for long term disease, when you're caring for someone over weeks, months, years, your immune system is compromised for an extended period and it's easy to start getting sick more frequently in spite of good eating, handwashing, exercise, etc.
So, make sure you're taking care of yourself too. You need it.
Daughter of Dad with Stage IV CC